Shulou(Shulou.com)06/02 Report--

In "Architects must know Ali's Middle Taiwan Strategy and Micro Services", it has been stated that the choice of SpringCloud for micro service architecture to achieve China Taiwan strategy, so the following introduction of some content of SpringCloud, SpringCloud has been out for many years, a lot of online materials, here recommended programmer DD blog http://blog.didispace.com/ about Spring Cloud micro service components and so on to do a very detailed introduction Suitable for beginners to learn.

Spring Cloud is based on Spring Boot, so students who are still using SpringMVC should learn about Spring Boot first. First of all, Spring Cloud is a cloud application development tool based on Spring Boot, which provides a simple development framework for configuration management, service discovery, circuit breaker, intelligent routing, micro-agent, control bus, global lock, decision campaign, distributed session and cluster state management involved in JVM-based cloud application development.

Spring Cloud does not repeat manufacturing wheels, it just combines the more mature service frameworks developed by various companies that can stand the actual test, and shields the complex configuration and implementation principles through Spring Boot style re-encapsulation, and finally leaves a set of distributed system development kits that are easy to understand, easy to deploy and easy to maintain.

Spring Cloud family bucket

The above picture is the Spring Cloud family bucket, all-inclusive, like water and electricity, related to the development of the square page.

From the beginning of its design, Spring Cloud considered the functions needed for the evolution of the architecture of most Internet companies, such as service discovery registration, configuration center, message bus, load balancing, circuit breakers, data monitoring and so on.

The first is the component of core service governance (service registration and discovery) Spring Cloud Eureka

Eureka is an open source Netflix product that provides service registration and discovery. Eureka is a service center that registers all the services that can be provided to manage it. Other callers go to the registry to get when they need it, and then make calls, avoiding direct calls between services and facilitating subsequent horizontal expansion, failover, and so on. As shown below:

Of course, the suspension of such an important component as the service center will affect all services, so it is necessary to set up an Eureka cluster to maintain high availability. At least two are recommended in production. With the increasing traffic of the system, it is necessary to expand a service according to the situation. Eureka has provided load balancing function, and you only need to add corresponding server instances. So what if an instance fails during the operation of the system? Eureka content has a heartbeat detection mechanism. If an instance does not communicate within a specified period of time, it will be automatically deleted, so as to prevent an instance from dropping and affecting the service.

Therefore, the use of Eureka automatically has the functions of registry, load balancing and failover.

Of course, there is another implementation component, Spring Cloud Consul, which is not covered here.

With the increasing number of micro-services, each micro-service has its own corresponding profile. In the process of research and development, there are test environment, UAT environment and production environment, so each microservice corresponds to at least three different environment configuration files. With so many configuration files, if you need to modify the configuration information of a public service, such as cache, database, etc., it will inevitably cause confusion, so you need to introduce another component of Spring Cloud: Spring Cloud Config.

Spring Cloud Config

Spring Cloud Config is a configuration management solution for distributed systems. It includes two parts: Client and Server. In fact, the Server side services all the configuration files, and the service instance of the configuration file needs to go to Config Server to obtain the corresponding data. Organize all the configuration files together to avoid the fragmentation of the configuration files.

If the configuration file is changed while the service is running, the service will not get the latest configuration information, and Refresh needs to be introduced to solve this problem. Configuration files can be reloaded while the service is running, and when all configuration files are stored in the configuration center, the configuration center becomes a very important component. If there is a problem with the configuration center, it will lead to catastrophic consequences, so it is recommended to cluster the configuration center in production to support the high availability of the configuration center.

Hystrix

In micro-service architecture, there are usually multiple service layer invocations, and the failure of basic services may lead to cascade failures, resulting in the unavailability of the whole system, which is called service avalanche effect.

As shown in the following figure: an is the service provider, B is the service consumer of A, and C and D are the service consumers of B. The unavailability of A causes the unavailability of B, and when the unavailability is enlarged to C and D like a snowball, the avalanche effect is formed.

In this case, it is necessary for the whole service organization to have the function of fault isolation to avoid a service hanging up and affecting the overall situation. Hystrix components play this role in Spring Cloud.

Hystrix will immediately notify the caller of the failure of the invocation in the case of N consecutive calls of a service, preventing the caller from waiting and affecting the overall service. The service is checked again during the Hystrix interval and will continue to be provided if the service is restored.

Hystrix Dashboard and Turbine

When a circuit breaker occurs, it needs a rapid response to solve the problem and avoid further spread of the fault, so the monitoring of the circuit breaker becomes very important. There are now two tools for circuit breaker monitoring: Hystrix-dashboard and Turbine.

Hystrix-dashboard is a tool for real-time monitoring of Hystrix. Through Hystrix Dashboard, we can directly see the request response time, request success rate and other data of each Hystrix Command. But if you only use Hystrix Dashboard, you can only see the service information in a single application, which is obviously not enough. We need a tool that allows us to aggregate data from multiple services in the system and display it on Hystrix Dashboard. This tool is Turbine. The effect of monitoring is as follows:

Spring Cloud Bus message bus

Although the Refresh solution can solve the problem of overloading configuration information during the operation of a single microservice, in real production, there may be more than N services that need to update the configuration. If you rely on manual Refresh each time, it will be a huge workload. At this time, Spring Cloud proposed another solution: Spring Cloud Bus.

Spring Cloud Bus connects distributed nodes through a lightweight message broker. This can be used in broadcast state changes (such as configuration changes) or other message instructions. One of the core ideas of Spring Cloud Bus is to extend Spring Boot applications through distributed initiators, and it can also be used to establish communication channels between one or more applications. Currently, the only way to do this is to use the AMQP message broker as a channel.

Spring Cloud Bus is a lightweight communication component that can also be used in other similar scenarios. With Spring Cloud Bus, when we change the configuration file and submit it to the version library, the Refresh of the corresponding instance will be automatically triggered. The specific workflow is as follows:

Service gateway

In the micro-service architecture mode, the number of instances of back-end services is generally dynamic, so it is difficult for clients to find the access address information of dynamically changed service instances. Therefore, in order to simplify the front-end invocation logic in micro-service-based projects, API Gateway is usually introduced as a lightweight gateway, and related authentication logic is also implemented in API Gateway to simplify the complexity of calling each other between internal services.

The technology that supports API Gateway landing in Spring Cloud system is Zuul. Spring Cloud Zuul routing is an indispensable part of micro-service architecture, which provides edge services such as dynamic routing, monitoring, resiliency, security and so on. Zuul is a load balancer based on JVM routing and server produced by Netflix. Its specific function is to forward, receive and forward all internal and external client calls. Zuul can be used as a unified access entry for resources, and you can also do some permission verification and other similar functions in the gateway.

Link tracking

With more and more services, the analysis of the call chain will become more and more complex, such as the call relationship between services, the call chain corresponding to a request, the consumption time between calls, and so on. In the actual use, we need to monitor the indicators of communication between services and services, these data will be the main basis for us to improve the system architecture. So distributed link tracking becomes very important, and Spring Cloud also gives a specific solution: Spring Cloud Sleuth and Zipkin.

Spring Cloud Sleuth provides link tracing for calls between services. Through Sleuth, you can clearly understand which services a service request has gone through and how long it takes for each service to process. This makes it very convenient for us to sort out the invocation relationship between microservices. Distributed link tracking needs the combination of Sleuth+Zipkin to achieve, of course, the realization of link tracking is also a tripartite open source solution, if the function of zipkin is very simple, the graphical ability is not strong, so you can try other schemes, such as the more mature framework of pinpoint.

Feign

Declarative remote scheduling component.

Ribbon

Load balancing component

Spring Cloud Data Flow

Big data operation component, which is a substitute for Spring XD and a hybrid computing model, can manipulate data flow through the command line.

Spring Cloud Task

The component is based on Spring Tsak and provides the functions of task scheduling and task management.

The above only describes the very important content that is often used. The general technology stack is SpringCloud + GitLab+Jinkins for the development of common services, continuous integration and deployment of CI. Later, you can upgrade the deployment with SpingCloud + GitLab+Jinkins+Docker containerization, and further upgrade to automatic container layout with SpingCloud + GitLab+Jinkins+Docker+k8s. The level of difficulty here is completely different, and each component involves a lot of content. How to split the traditional business into micro-services will be discussed next time.

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